1. Field of the Invention
This invention relates a method for continuous roasting of food materials and an apparatus therefor. More particularly, it relates to a novel improvement for the continuous frying, drying and concentration of food materials.
2. Related Art
A common method for pan-frying food materials comprises feeding a small amount of oil in a heatged pan or frying pan and then heating the food materials together with the oil. When pan-frying, which is one of the easiest cooking operations, is employed at home, a small amount of food materials can be readily fried in a frying pan without requiring much labor or attention. On the other hand, the currently employed methods for cooking a large amount of food materials can be roughly classified into the following three types depending on the shape of the pan and the cooking process.
Namely, "Atarashii Shokuhin Kako Gijutsu to Sochi (New Techniques and Apparatuses for Processing Foods)" published by Sangyo Chosa-kai (Jan. 10, 1991) discloses an "escargot" type fryer, a "cup" type fryer and a fryer provided with an agitator. In the first method of the "escargot" type fryer, a pan with a "snail"-shaped bottom is slowly rotated horizontally so that food materials are slowly moved toward the outer peripheral of the pan under heating and then once collected therein. Subsequently, the pan is further rotated and inclined at a definite angle. Then the food materials drop into the outer periphery of the pan owing to the gravity of the food materials per se. In this step, the direction of dropping can be altered with the use of small paddles and thus the food materials can be agitated. Also, the food materials drop a specific distance while giving off the excessive vapor therefrom. In this method, the above procedures are carried out repeatedly. In the second method, the "cup" type pan is equipped on the inner periphery with one or two plates or projections for carrying up the food materials. Since the cup type fryer has no lid in usual, it is somewhat inclined upward in rotational frying. The food materials are slightly carried up from the bottom of the pan by the plate(s) or projection(s) on the inner periphery and turned upside down, thus being agitated. In the method of the fryer provided with an agitator, a pan is not rotated but the food materials are fried with a paddle- or ribbon-type agitator under a planetary motion. Pans of this type are disclosed in, for example, JP-B-57-38255 (the term "JP-B" as used herein means an "examined Japanese patent publication") and JP-A-U-62-136193 (the term "JP-A-U" as used herein means an "unexamined published Japanese utility model application"). In the field of food processing, it has been a practice to roast food materials by using the fluidized gas bed system or the fluidized rotary bed system in the intermediate or final stage of the processing. In the fluidized gas bed system, powdery materials are suspended and fluidized by hot air supplied onto a rectifier such as a porous plate and dried by vigorously mixing with the hot air. In the rotary fluidized bed system, a fluidized bed is divided into small portions by rotating a compartmented rotor and food materials are fluidized exclusively in each compartment.
The conventional methods for continuous roasting with the constructions as described above suffer from the following problems.
That is to say, in each of the "escargot" type fryer, the "cup" type fryer and the fryer provided with an agitator, food materials should be replaced each time, which makes the continuous roasting difficult. In these cases, moreover, the qualities of the fried products varies from batch to batch.
In these fryers, furthermore, a large amount of food materials are agitated while being in contact with each other and, therefore, soft materials or softened ones would lose their shapes. In the case of the fluidized gas bed system, continuous roasting can be hardly performed. In addition, it is difficult to suspend and fluidized some food materials in hot air due to the form, size, etc. thereof. On the other hand, food materials in any form can be processed by the rotary fluidized bed system. However, it is needed in this case to employ a complicated and, in its turn, expensive apparatus.